Anodic Voltammetry of Xanthine, Theophylline, Theobromine and Caffeine at Conductive Diamond Electrodes and Its Analytical Application

Abstract

Boron-doped diamond (BDD) electrodes were used to examine the electrochemical oxidation of xanthine and its naturally occurring N-methyl derivatives, theophylline, theobromine and caffeine. Voltammetric studies showed that the mechanism of the overall reaction is similar to that of the oxidation of purine derivatives at the pyrolytic graphite electrode. The effects of pH, concentration and potential sweep rate on the voltammetric response were thoroughly investigated, and it was found that BDD exhibits excellent behavior, in terms of very well-defined, reproducible oxidation peaks, for xanthine, theophylline, theobromine and caffeine determination. The results enabled the measurement of the oxidation peak current to be used as the basis for a simple, accurate and rapid method for determining the investigated compounds, within a concentration range of 1 to 400 μM for theophylline, theobromine and caffeine, and of 1 to 100 μM for xanthine. Promising results were obtained for caffeine determination in real samples of commercially available products, without separation from the matrix.